Antenna having dipoles inductively coupled to transmission line



March 10, 1970 WELLS 3,500,471

ANTENNA HAVING DIPOLES INDUCTIVELY COUPLED T0 TRANSMISSION LINE Filed June 9, 1966 3 Sheets-Sheet 1 H MAGNETIC FIG. I

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TR AUER.

DRIVE ELEMENT DIPOLE REFLECTOK Dl P0 LE DI REQTOR INVENTOR. DQMAkD H. News 1 1 SW gm March 10, 1970 WELLS 3,500,471

ANTENNA HAVING DIPOLES INDUC'IIVELY COUPLED TO TRANSMISSION LINE Filed June 9. 1966 v 3 Sheets-Sheet z i 'fld-uuas or mane-m. FO E I YCURKENT-FLOLO m mus ELEMENT NoM-RADIAHNG RANSMISSIQN NA Emma um: DRIVE ELEMENT FIG. 4

' INVENTOR. 6 DONALD H- WEI-l3 o x P Mu f M ATTOKMEQS March 10, 1970 n. H. WELLS Filed June 9. 1966 3 Sheets-Sheet 3 FIG. 7

EOJQ l -52 ac, f f L 1 L 1 3+ I 4 mvsw'rox. L 38 a mm HMaus x) g a I United States Patent US. Cl. 343-814 1 Claim ABSTRACT OF THE DISCLOSURE An antenna system for commercial television frequencies utilizing dipole elements inductively coupled to a transmission line. A first dipole includes two spaced-apart conductors electrically coupled by a U-shaped stub. A second dipole is spaced from the first dipole to establish a standing wave which is inductively coupled to the transmission line to energize a load.

This invention relates to antennas and more particularly to a broad band antenna system.

It is an object of the invention to produce an antenna system capable of operating in the commercial television frequency band widths.

Another object of the invention is to produce an antenna system utilizing antenna dipole elements which are magnetically or inductively coupled to an associated transmission line drive element.

Still another object of the invention is to produce a broad band antenna system which is rugged in construction and may be readily and economically manufactured.

Still a further object of the invention is to produce a broad band antenna system which has higher gain characteristics than the conventional antenna systems.

These and other objects and advantages of the invention may be achieved by a preferred embodiment of the invention which comprises a non-radiating transmission line drive element, a first dipole element reactively coupled to the transmission line drive element, a second dipole element spaced from the first dipole element to establish a standing wave in space between the dipole elements, whereby the energy of the standing wave is inductively coupled to the transmission line drive element, and means for coupling the transmission line drive element to a load.

Other objects and advantages of the invention will become readily apparent from reading the following detailed description of several embodiments of the invention when considered in the light of the accompanying drawings, in which:

FIGURE 1 is a diagrammatic illustration of the vector relationship of a transverse electromagnetic traveling wave;

FIGURES 2a, 2b, 2c, and 2d are diagrammatic illustrations showing the establishment in space of a standing electromagnetic wave in association with a conventional Yagi-type antenna;

FIGURE 3 is a diagrammatic illustration of an antenna utilizing a non-radiating transmission line drive element;

FIGURE 4 illustrates the electric and magnetic field relationships of the antenna structure of FIGURE 3;

FIGURE 5 is a diagrammatic perspective view of an antenna system employing the novel features of the invention;

FIGURE 6 is a side view of the antenna system illustrated in FIGURE 5; and

FIGURE 7 is a plan view of a hybrid antenna system capable of operating over the commercial television band widths.

In order to completely understand the instant invention, it is considered necessary to review the nature of electromagnetic radiation. A transverse electromagnetic traveling wave is a wave in which both the electric and magnetic fields are transverse to each other and to the direction of travel. The vector relationship of these fields is sliown in FIGURE 1. The velocity of propagation or speed of travel of such a wave is equal to the speed of light and and, the frequency or wave length is the distance between successive points of the same electrical phase in the wave. As a general rule, it may be stated that power may not be taken from a traveling wave unless it is first acted upon in such a manner as to create a standing wave.

Standing waves are established as the result of two waves of the same frequency traveling in opposite directio'ns. Standing waves in space result when a signal is reflected back toward its direction of source. Standing waves on a transmission line exist when a signal is reflected back from a load, and it is necessary for a standing wave to exist on an antenna element if it is to radiate or receive power. Power may be taken from a standing wave because, as its name implies, it is standing still in one place, rather than traveling at the speed of light, as is the case with the traveling wave, and the fields associated with the wave are alternately reversing their polarity at the speed of the waves frequency.

As a general rule, it may be stated that it is necessary to create a standing wave before power may be taken from an incoming wave front or traveling wave.

With the above in mind, let use examine a conventional Yagi-type antenna array as illustrated in FIGURE 2 and observe the operation as a traveling wave arrives. For simplicity of discussion, we will not consider standing waves that exist on the dipole elements, but rather will look only at the waves that exist in space as a result of the parasitic elements. Since the parasitic elements of the Yagi array are not terminated in a load, all of the energy received by the elements will be returned to space. The incoming traveling wave is represented by the sine wave A and the arrows indicate the direction of travel As the wave A arrives at the dipole director, it impresses a volt-' age thereon. This energy is returned to space in the form of a traveling wave represented by the sine wave B. Since the dipole element, by itself, is bi-directional, half of the power will travel to the right and half of the power will travel to the left, as indicated by the arrows. Two waves, A and B, will travel until they meet the reflector dipole, disregarding the effect of the driven dipole, where they are reflected back toward the right, as represented by the sine wave C. The resultants of these traveling waves are the standing waves D and E. D is a resultant of one half of the wave B, and the wave A, traveling in the opposite direction, and E is the resultant of the waves A and B traveling in the opposite direction of the wave C.

We can see from the above that we have satisfied the first requirement for taking power from the traveling wave without considering the function of the driven dipole, in that, a standing Wave has been established. Since a standing wave exists in space in the antenna arrangement shown in FIGURE 2, a driven dipole element is not necessary to take power from the antenna array. A section of transmission line arranged to provide a mutual flux linkage with the magnetic field of the standing wave will satisfy the requirements for the driven means quite well, and has many added advantages over the driven dipole element. This arrangement is shown in FIGURE 3.

In place of a driven dipole, as in the case of an antenna operating in the E field (electric), a section of transmission line shorted at both ends is utilized. Such an arrangement provides inductive coupling between the transmission line drive element and the magnetic field of the standing wave. Any value of impedance from a very low value to a very high value may be found at points along the transmission line drive element, making a very precise impedance match to an associated transmission line quite easily obtained. Since the currents are balanced in thetransmission line drive element, this element will not radiate or receive power from a traveling wave, but is sensitive only to the mangetic field of a standing wave. This results in a very high signal to noise ratio since a standing wave will be established only at the operating frequency of the antenna, and then only when the signal arrives from a proper direction.

FIGURE 4 is a diagrammatic representation of the manner in which the unwanted signal discrimination is accomplished. Since the antenna array has the same directional characteristic when transmitting as When receiving, a signal arriving from the back side, even though it produces a standing Wave on the antenna dipole elements, will be retransmitted in the form of a traveling wave in its original direction, and no standing wave will result.

The above description illustrates the general operating characteristics of a free space standing wave magnetic drive antenna. However, the band width characteristics of such an antenna are basically narrow and the frequency is typically determined by the length of the transmission line drive element.

It has been found that by coupling a resonate load to the transmission line drive element, the band width is greatly increased. A preferred system for accomplishing the desired objective is illustrated in the antenna shown in FIGURES 5 and 6. The antenna therein illustrated embodies a non-radiating transmission line drive element consisting of a pair of spaced electrical conductors and 12. An antenna dipole element, generally indicated by reference numeral 14 is insulatingly supported in space relation by bracket members, not shown, to the transmission line drive element. The dipole element 14 is typically comprised of a pair of conducting arms 16 and 18, the inner ends of which are respectively connected to each other through a loading stub 20. The loading stub 20 is generally U-shaped and has two leg portions which extend parallel to the respective ones of the electrical conductors 10 and 12 of the transmission line drive element.

A unitary dipole element 22 is insulatingly supported in space relation by brackets, not shown, to the transmission line drive element. The dipole elements 14 and 22 are suitably formed of electrically conductive material such as for example, aluminum tubing.

its energy on the dipole elements 14 and 22. A majority of the energy is retransmitted back toward the signal source to thereby establish a standing wave in the manner set forth hereinbefore. A small portion of the energy is received by the dipole element 14 and creates a flow of current i The current i will flow through the arms 16 and 18 and the associated loading stub 20 in the direction illustrated by the arrows in FIGURE 5 during one half cycle and in an opposite direction during the next succeeding half cycle. The magnetic field associated with the current flow I induces a current i to flow in the conductors 10 and 12 of the transmission line drive element. This reactive coupling between the dipole element 14 and the transmission line drive element imparts to the antenna system broad band characteristics. The remainder of the energy received by the dipole element 14 is returned to space in the form of a traveling wave. Since this Wave is traveling in a direction opposite to the incoming traveling wave from the signal source and the dipole element 22, a standing wave will be established. The established standing wave remains in one position in space and the alternations in the polarity of the associated magnetic field induces a current to flow in the conductors 10 and 12 of the transmission line drive element to reinforce the current i previously discussed, thereby producing a highly efficient broad band antenna system.

With reference to FIGURE 7, there is shown a hybrid antenna system having extremely broad band characteristics. More specifically, the system illustrated has been found to operate over the 54-108, 174-216, and 470-890 megacycles per second band widths. The antenna consists of a supporting boom which is adapted to be held in a substantially rigid horizontal position on a mast (not shown) in the conventional manner.

The antenna consists of a dipole element 32 secured adjacent one end of the boom 30. A pair of folded dipoles 34 and 36 are positioned on the boom 30 in spaced relation with respect to one another and from the dipole element 32. The terminals 38 and 40 of the folded dipole 34 are connected to respective conductors 42 and 44 of a transmission line drive element. The terminals 46 and 48 of the folded dipole element 36 are connected respectively to the conductors 44 and 42 of the transmission line drive element. It will be observed that the conductors 42 and 44 extend in spaced parallel relationship to the boom 30.

A pair of open stubs 50 and 52 are connected to the conductors 44 and 42, respectively, of the transmission line drive element in spaced relation from the folded dipole element 36. Spaced from the open stubs 50 and 52, there is a dipole element 54 suitably supported by the boom 30.

In spaced relation from the dipole 54, a loaded dipole element 56 is mounted on the boom. The dipole element 56 is similar in structure and operation to the element illustrated and described with reference to the embodiment illustrated in FIGURES 5 and 6. It will be noted that the legs '57 and 58 of the loading stub are arranged to extend in spaced parallel relation to the conductors 44 and 42 of the transmission line drive element.

In spaced relation from the loaded dipole element 56, there is disposed a pair of spaced apart dipole elements 60 and 62. A loaded dipole element 64 similar to the element.56 is mounted on the boom 30 in such fashion that the legs 65 and 66 of the loading stub are arranged to extend in spaced parallel relation to the conductors 44 and 42 of the transmission line drive element.

Dis-posed in spaced relation from the loaded dipole element 64, there is positioned a dipole 68 suitably secured to the boom 30. A pair of open stubs 70 and 72 are spaced from the dipole element 68 and electrically coupled to the conductors 44 and 42, respectively, of the transmission line drive element.

Another dipole element 74 is spaced from the open stubs 70 and 72 and suitably secured to the boom 30. Spaced from the dipole element 74, there is another pair of open stubs 76 and 78 which are suitably electrically connected to the conductors 44 and 42, respectively, of the transmission line drive element.

A series of spaced dipole elements 80, 82, 84, 86, and 88 are located forwardly of the open stubs 76 and 78 and suitably secured to the boom 30.

The forward ends of the conductors 42 and 44 of the transmission line drive element connected to a transmission line indicated by reference numeral 90 which in turn is connected to a suitable load such as a television receiver, for example.

In a practical television antenna which is proved to be particularly efiective'for television reception, the following dimensions were used:

Length of each arm of loaded dipole element 56 25 /2 Length of the loading arms 57 and 58 7 Length of dipole element 60 26 Length of dipole element 62 25 Length of each arm of loaded dipole element 64 25 /2 Length of the loading arms 65 and 66 7 Length of dipole element 68 24 Length of open stubs 70 and 72 5 Length of dipole element 74 12 Length of open stubs 76 and 78 6 Length of dipole element 80 10 Length of dipole element 82 9 Length of dipole element 84 8 Length of dipole element 86 7 Length of dipole element 88 6 Distance between dipole element 32 and folded dipole element 34 25% Distance between folded dipole element 34 and folded and dipole element 36 Distance between folded dipole element 36 and the connection of open stubs 50 and 52 to conductors 44 and 42 8 Distance between the connection of open stubs 50 and 52 to conductors 44 and 42 and dipole element 54 Distance between dipole element 54 and the arms of loaded dipole 56 Distance between the arms of loaded dipole 56 and dipole element 60 8 Distance between dipole element 60 and dipole element 62 7% Distance between dipole element 62 and the arms of loaded dipole 64 7% Distance between the arms of loaded dipole element 64 and dipole element 68 2 /8 Distance between dipole element 68 and the connection of open stubs 70 and 72 to conductors 44 and 42 6% Distance between the connection of open stubs 70 and 72 to conductors 44 and 42 and dipole element 76 1% Inches Distance between dipole element 76 and the connection of open stubs 7'6 and 78 to conductors 44 and 42 and dipole element 80 6 Distance between dipole element 80 and dipole element 82 8% Distance between dipole element 82 and dipole element 84 5 /2 Distance between dipole element 84 and dipole element 86 5% Distance between dipole element 86 and dipole element 88 4% Distance between conductors 42 and 44 2% All of the above distances are measured from center of diameter of one element to the center of diameter of the following element.

According to the patent statutes, I have explained the principles and mode of operation of my invention, and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claim, the invention may be practiced otherwise than as specifically illustrated and described.

What I claim is:

1. An antenna system comprising a non-radiating, parallel wire transmission line drive element;

a first dipole transversely spaced from and reactively coupled to said transmission line drive element,

said first dipole comprising two spaced-apart collinear members electrically coupled together by a generally U-shaped loading stub having leg portions extending parallel to said transmission line drive element;

a secondary unitary dipole spaced from said first dipole to establish a standing wave in space between said dipoles,

whereby the energy of the standing Wave is inductively coupled to said transmission line drive element; and

means for coupling said transmission line drive element to a load.

References Cited UNITED STATES PATENTS 2,433,804 12/1947 Wolff 343811 2,716,703 8/1955 Kane 3438l5 ELI LIEBERMAN, Primary Examiner US. Cl. X.R. 3438l5 

